The present invention relates to hangers for supporting concrete formwork and, more particularly, to hangers for supporting concrete formwork associated with I beams and including cantilevered sections.
In the design of bridges, it is common to provide a sidewalk, fascia or similar auxiliary concrete structure to extend along and adjoin the principal concrete roadway, overpass or other concrete installation. Typically, such auxiliary structures are located outside the I beams comprising the bridge superstructure. Consequently, it is necessary to provide formwork which is supported by these outside I beams and, in turn, supports formwork which is cantilevered outwardly from these I beams.
For example, the Boll et al. U.S. Pat. No. 3,782,676 discloses a formwork hanger which is specially designed to support formwork that is cantilevered outwardly from an I beam. The hanger includes an inboard bracket having a downwardly extending portion that engages the inside edge of the upper I beam flange, an outside bracket that rests upon the upper surface of the I beam flange, and a connecting rod which joins the brackets togther and spaces them at a predetermined distance appropriate for a specific flange width. Both of the brackets are U-shaped, and the inside bracket includes a vertically extending channel which is shaped to receive a formwork support bolt in a substantially vertical orientation. The hanger also includes a third bracket, attached to the connecting rod by an L-shaped bar and positioned adjacent to the outside bracket, which includes a vertical passage for supporting a formwork support bolt in a substantially vertical orientation.
The outside bracket includes a through bore that is disposed at approximately a 45.degree. angle to the supporting I beam flange and is sized to receive a relatively long formwork support bolt. The angled formwork support bolt is attached at its lower end to a triangular member which abuts the vertical web of the I beam and extends horizontally outwardly therefrom to support the formwork that is cantilevered beyond the superstructure.
Another type of hanger is disclosed in the Torbet et al. U.S. Pat. No. 3,981,469. That hanger includes a pair of identically-shaped brackets spaced apart by an upper threaded rod which absorbs tension forces in use and a lower rod which butts the two brackets to absorb compression forces in use. Each connecting bracket has an inverted L-shape which includes an upper overhanging portion having a bore for supporting a vertically oriented formwork support bolt. In addition, each bracket includes an angled section located at the juncture of the vertical and horizontal components of the J-shape and having a slot for receiving a formwork support bolt at approximately a 45.degree. angle.
A disadvantage with both of these types of hangers is that they lack the adjustability which would enable them to be used with more than one width of I beam flange. In the Boll et al. device, there is no mechanism whatsoever for adjusting the spacing between the inside and outside brackets, so that each hanger must be designed specifically for a particular I beam flange width. With the Torbet et al. device, it might be possible to substitute connecting rods of different lengths to vary the spacing between the inside and outside brackets of that device, but such an adjustment is not disclosed in the patent.
A second disadvantage of such devices is that both lack a mechanism for adjusting the angular orientation of the longer support bolts held by the hanger. In some formwork support structure applications, for example, it may be perferable to provide a longer support bolt at angle other than 45.degree.. In such an event, neither of the aforementioned hanger constructions would be useful.
Accordingly, there is a need for a formwork support hanger in which the inside and outside brackets can be adjusted to vary the space between them to accommodate a variety of I beam flange widths, so that a single hanger design can be used in virtually any application. Furthermore, there is a need for a formwork support hanger in which the outside bracket is capable of supporting a formwork support bolt at angles other than 45.degree..